Abstract 12425: Sirt2 Mediated-Deacetylation Regulates Cellular Iron Homeostasis

Background: Sirtuins (SIRTs) are NAD+-dependent deacetylases and critical regulators of energy metabolism and response to oxidative stress in the heart. Iron is essential for these processes but is toxic when present in excess. Thus, SIRTs may regulate iron levels to ensure adequate supply of this element for their biological functions. SIRT2 is among the least characterized SIRTs and is mainly present in the cytoplasm. We hypothesized that SIRT2 might be required for cellular iron homeostasis. Methods and Results: Iron content was significantly lower in SIRT2-/- mouse embryonic fibroblasts (MEFs) compared to SIRT2+/+ MEFs (non-heme iron: 0.073 vs. 0.060 nmol/μg protein, p=0.02). Gene expression of ferroportin-1 (FPN1), the major cellular iron exporter, was significantly increased in SIRT2-/- MEFs. Similarly, silencing SIRT2 in HepG2 cells decreased cellular iron levels and increased FPN1 expression, indicating that enhanced FPN1 in SIRT2 knockout or knockdown condition increases iron export and reduces cellular iron. To investigate the underlying mechanism, we focused our studies on nuclear factor (erythroid-derived 2)-like 2 (Nrf2), a known regulator of FPN1. Our results demonstrated that Nrf2 is upregulated and translocates into the nucleus in SIRT2-/- MEFs and knocking down Nrf2 in SIRT2-/- MEFs reverses iron deficiency and FPN1 expression. Furthermore, Nrf2 is acetylated by P300/CBP and can be deacetylated by SIRT2. Finally, to confirm the role of SIRT2 in iron regulation, cellular heme and non-heme iron in the heart (major iron-consuming organ) and liver (major iron-storage organ) were measured in wild type (WT) and SIRT2-/- mice. Heme and non-heme iron content were significantly decreased in SIRT2-/- mouse livers compared to WT livers (heme: 2.25 vs. 1.65 nmol/mg protein, p=0.002; non-heme iron: 0.073 vs. 0.064 nmol/μg protein, p=0.03). Furthermore, heme levels were also significant decreased in the heart, while non-heme iron was not significantly altered. Conclusions: Our results suggest that SIRT2 regulates cellular iron homeostasis by deacetylating NRF2 and altering iron export through FPN1.

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Abstract 92: Sirtuin 2 mediated-deacetylation regulates cellular iron homeostasis

Circulation Research ◽

10.1161/res.115.suppl_1.92 ◽

2014 ◽

Vol 115 (suppl_1) ◽

Author(s):

Xiaoyan Yang ◽

Athanassios Vassilopoulos ◽

Seong-Hoon Park ◽

David Gius ◽

Hossein Ardehali

Keyword(s):

Iron Content ◽

Hepg2 Cells ◽

Iron Homeostasis ◽

Underlying Mechanism ◽

Heme Iron ◽

Iron Storage ◽

Cellular Iron ◽

Non Heme Iron ◽

Cellular Iron Homeostasis ◽

Iron Export

Background: Sirtuins (SIRTs) are NAD+-dependent deacetylases, which regulate energy metabolism and response to oxidative stress in the heart. Iron is essential for these processes but is toxic when present in excess. However, whether SIRTs are involved in maintaining cellular iron homeostasis is not known. SIRT2 is among the least characterized SIRTs and is mainly present in the cytoplasm. We hypothesized that SIRT2 is required for cellular iron homeostasis. Methods and Results: Iron content was significantly lower in SIRT2-/- mouse embryonic fibroblasts (MEFs) compared to SIRT2+/+ MEFs (non-heme iron: 0.073 vs. 0.060 nmol/μg protein, p=0.02), andlevels of ferroportin-1 (FPN1), the major cellular iron exporter, was significantly increased in SIRT2-/- MEFs. Similarly, silencing SIRT2 in HepG2 cells decreased cellular iron levels and increased FPN1 expression, indicating that enhanced FPN1 with SIRT2 downregulation drove iron export and caused a reduction in cellular iron levels. Furthermore, iron export assays showed that iron export was increased in HepG2 cells with SIRT2 knockdown. To investigate the underlying mechanism, we focused our studies on nuclear factor (erythroid-derived 2)-like 2 (Nrf2), a known regulator of FPN1. Our results demonstrated that Nrf2 is upregulated and translocates into the nucleus in SIRT2-/- MEFs and knocking down Nrf2 in SIRT2-/- MEFs reverses iron deficiency. Furthermore, Nrf2 is acetylated by P300/CBP and can be deacetylated by SIRT2. Finally, to confirm the role of SIRT2 in iron regulation, cellular heme and non-heme iron in the heart (major iron-consuming organ) and liver (major iron-storage organ) were measured in wild type (WT) and SIRT2-/- mice. Heme and non-heme iron content were significantly decreased in SIRT2-/- mouse livers compared to WT livers (heme: 2.25 vs. 1.65 nmol/mg protein, p=0.002; non-heme iron: 0.073 vs. 0.064 nmol/μg protein, p=0.03). Furthermore, heme levels were also significant decreased in the heart, while non-heme iron was not significantly altered. Conclusions: Our results suggest that SIRT2 regulates cellular iron homeostasis by deacetylating NRF2 and altering iron export through FPN1.

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Ferrosomes are iron storage organelles formed by broadly conserved gene clusters in bacteria and archaea

10.1101/2020.01.10.902569 ◽

2020 ◽

Author(s):

Carly R. Grant ◽

Arash Komeili

Keyword(s):

Iron Homeostasis ◽

Rhodopseudomonas Palustris ◽

Gene Clusters ◽

Iron Starvation ◽

Iron Storage ◽

Cellular Iron ◽

Conserved Gene ◽

And Function ◽

Related Proteins ◽

Cellular Iron Homeostasis

Cellular iron homeostasis is vital and maintained through tight regulation of iron import, efflux, storage, and detoxification1–3. The most common modes of iron storage employ proteinaceous compartments that are composed of ferritin or related proteins4,5. While lipid-bounded iron compartments have also been described, the basis for their formation and function remains unknown. Here, we focus on one such compartment, the ferrosome, which had been previously observed in the anaerobic bacterium Desulfovibrio magneticus6. We identify three ferrosome-associated (Fez) proteins, encoded by a putative operon, that are associated with and responsible for forming ferrosomes in D. magneticus. Fez proteins include FezB, a P1B-6-ATPase found in phylogenetically and metabolically diverse species of bacteria and archaea with anaerobic lifestyles. In the majority of these species, two to ten genes define a cluster that encodes FezB. We show that two other species, Rhodopseudomonas palustris and Shewanella putrefaciens, make ferrosomes in anaerobic conditions through the action of their six-gene fez operon. Additionally, we find that the S. putrefaciens fez operon is sufficient for ferrosome formation in Escherichia coli. Using S. putrefaciens as a model, we find that ferrosomes likely play a role in the anaerobic adaptation to iron starvation. Overall, this work establishes ferrosomes as a new class of lipid-bounded iron storage organelles and sets the stage for studying ferrosome formation and structure in diverse microorganisms.

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Cellular Iron Homeostasis and Therapeutic Implications of Iron Chelators in Cancer

Current Pharmaceutical Biotechnology ◽

10.2174/138920101512141202111915 ◽

2014 ◽

Vol 15 (12) ◽

pp. 1125-1140 ◽

Cited By ~ 15

Author(s):

Mohsin Raza ◽

Sankalpa Chakraborty ◽

Monjoy Choudhury ◽

Prahlad Ghosh ◽

Alo Nag

Keyword(s):

Iron Homeostasis ◽

Iron Chelators ◽

Therapeutic Implications ◽

Cellular Iron ◽

Cellular Iron Homeostasis

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Biochemistry of mammalian ferritins in the regulation of cellular iron homeostasis and oxidative responses

Science China Life Sciences ◽

10.1007/s11427-020-1795-4 ◽

2020 ◽

Author(s):

Jianlin Zhang ◽

Xuehui Chen ◽

Juanji Hong ◽

Aifa Tang ◽

Yang Liu ◽

...

Keyword(s):

Iron Homeostasis ◽

Cellular Iron ◽

Cellular Iron Homeostasis ◽

Oxidative Responses

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IRONOMYCIN KILLS DIFFUSE LARGE B‐CELL LYMPHOMA CELLS BY TARGETING CELLULAR IRON HOMEOSTASIS

Hematological Oncology ◽

10.1002/hon.79_2881 ◽

2021 ◽

Vol 39 (S2) ◽

Author(s):

J. Devin ◽

T. Cañeque ◽

Y.‐L. Lin ◽

L. Mondoulet ◽

J.‐L. Veyrune ◽

...

Keyword(s):

B Cell ◽

Iron Homeostasis ◽

Cell Lymphoma ◽

B Cell Lymphoma ◽

Lymphoma Cells ◽

Cellular Iron ◽

Large B Cell Lymphoma ◽

Cellular Iron Homeostasis ◽

Large B Cell

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Overexpression of mitochondrial ferritin causes cytosolic iron depletion and changes cellular iron homeostasis

Blood ◽

10.1182/blood-2004-07-2722 ◽

2005 ◽

Vol 105 (5) ◽

pp. 2161-2167 ◽

Cited By ~ 97

Author(s):

Guangjun Nie ◽

Alex D. Sheftel ◽

Sangwon F. Kim ◽

Prem Ponka

Keyword(s):

Iron Homeostasis ◽

Rna Binding ◽

Binding Activity ◽

Intracellular Iron ◽

Free Radical Damage ◽

Iron Regulatory Proteins ◽

Cellular Iron ◽

Cellular Iron Uptake ◽

A Cell ◽

Cellular Iron Homeostasis

AbstractCytosolic ferritin sequesters and stores iron and, consequently, protects cells against iron-mediated free radical damage. However, the function of the newly discovered mitochondrial ferritin (MtFt) is unknown. To examine the role of MtFt in cellular iron metabolism, we established a cell line that stably overexpresses mouse MtFt under the control of a tetracycline-responsive promoter. The overexpression of MtFt caused a dose-dependent iron deficiency in the cytosol that was revealed by increased RNA-binding activity of iron regulatory proteins (IRPs) along with an increase in transferrin receptor levels and decrease in cytosolic ferritin. Consequently, the induction of MtFt resulted in a dramatic increase in cellular iron uptake from transferrin, most of which was incorporated into MtFt. The induction of MtFt caused a shift of iron from cytosolic ferritin to MtFt. In addition, iron inserted into MtFt was less available for chelation than that in cytosolic ferritin and the expression of MtFt was associated with decreased mitochondrial and cytosolic aconitase activities, the latter being consistent with the increase in IRP-binding activity. In conclusion, our results indicate that overexpression of MtFt causes a dramatic change in intracellular iron homeostasis and that shunting iron to MtFt likely limits its availability for active iron proteins.

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